Bump mypy from 0.800 to 0.812

Bumps [mypy](https://github.com/python/mypy) from 0.800 to 0.812.
- [Release notes](https://github.com/python/mypy/releases)
- [Commits](python/mypy@v0.800...v0.812)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

test-requirements.txt

@@ -64,7 +64,7 @@ mypy-extensions==0.4.3 ; implementation_name == "cpython"
     #   -r test-requirements.in
     #   black
     #   mypy
-mypy==0.800 ; implementation_name == "cpython"
+mypy==0.812 ; implementation_name == "cpython"
     # via -r test-requirements.in
 outcome==1.1.0
     # via -r test-requirements.in